Someone asked me to explain how I used line weight (there are different ways to do it so don't take mine as some kind of standard), so I was a big derp, took a picture of my new pony and did some lines on it.

I do not do "variance" by light a lot, you'll often see me make thick lines facing the light or the upper side, better/different artists tend to thin the line towards the light and thicken it towards the shadow. You don't need to do that to show volume, imo

use 'inner contours' sparingly, especially if you want your drawn person to look smooth, it QUICKLY becomes wrinkles and cellulite if you draw many lines. Sometimes it's best to leave out a few lines, and "imply" them. It really depends on the look you want, and whether you are going to shade it.

The bottom right is me blabbering about some falloff logic I have. Again, this is my style of doing lines, it's not necessarily better than other styles, but I personally like a swooshy simple line.

Top right is also an attempt of describing not only dynamic size vs static, but also tight vs lazy line, but there are much better tutorials about avoiding lazy lines out there. I love a tight, tense line so that's what I strive for.

Thanks to Rudethefox for letting me know how to set up opencanvas to get more pressure dynamic effect. PS can't do this but you can hack your tablet driver settings to get a non-linear pressure response.. it helps but it's not necessary. All the pony lines were drawn with the same brush size, that's how dynamic it is even at light pressure. I don't press very hard. Always remember to install a tablet driver (don't use windows' default) and adjust the settings so they fit your way of drawing.